PCM wiring diagram JEEP GRAND CHEROKEE 2003 WJ / 2.G Workshop Manual

Programmable Communications Interface (PCI) data
bus network.
For diagnosis of the HSM, MHSM or the PCI data
bus, a DRBIIItscan tool and the proper Diagnostic
Procedures manual are recommended. The HSM or
MHSM cannot be repaired and, if faulty or damaged,
it must be replaced.
OPERATION
The MSM receives hard wired inputs from the
power seat switch and the potentiometers on each of
the driver side power seat motors. The MSM receives
messages over the PCI data bus from the Driver
Door Module (DDM) (memory switch status), the
Powertrain Control Module (PCM) (vehicle speed sta-
tus), and the Body Control Module (seat belt switch
status).The MSM will prevent the seat memory recall
function from being initiated if the driver side seat
belt is buckled, if the transmission gear selector lever
is not in the Park or Neutral positions, or if the vehi-
cle is moving.
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - HEATED SEAT
MODULE
Visually inspect the related wiring harness connec-
tors. Look for broken, bent, pushed out, or corroded
terminals. If any of the above conditions are present,
repair as necessary. If not, use a DRBIIItscan tool
and the proper Diagnostic Procedures Manual to test
the HSM or MHSM. For complete circuit diagrams,
refer toPower Seat Premium I/IIIin Wiring Dia-
grams.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the driver side front bucket seat from
the power seat track unit. Refer toBucket Seat
Track Adjusterin Body for the procedure.
(3) Lift the heated seat module off of the power
seat track and disconnect the power seat wire har-
ness connectors (Fig. 10).
(4) Remove the module from the bracket.
Fig. 9 Heated Seat Module Remove/Install
1 - NUT (4)
2 - SEAT CUSHION FRAME
3 - POWER SEAT TRACK
4 - STUD (4)
5 - MODULE
6 - BRACKET
Fig. 10 Heated Seat Module Remove/Install
1 - NUT (4)
2 - SEAT CUSHION FRAME
3 - POWER SEAT TRACK
4 - STUD (4)
5 - MODULE
6 - BRACKET
WJELECTRONIC CONTROL MODULES 8E - 11
MEMORY HEATED SEAT/MIRROR MODULE (Continued)

STARTING
TABLE OF CONTENTS
page page
STARTING
DESCRIPTION.........................29
OPERATION...........................30
DIAGNOSIS AND TESTING - STARTING
SYSTEM............................30
SPECIFICATIONS
TORQUE - STARTER...................35
STARTER MOTOR - GAS POWERED......35
STARTER MOTOR
DESCRIPTION.........................35
OPERATION...........................36DIAGNOSIS AND TESTING - STARTER
MOTOR .............................36
REMOVAL.............................37
INSTALLATION.........................38
STARTER MOTOR RELAY
DESCRIPTION.........................38
OPERATION...........................38
DIAGNOSIS AND TESTING - STARTER RELAY . 38
REMOVAL.............................39
INSTALLATION.........................40
STARTING
DESCRIPTION
An electrically operated engine starting system is
standard factory-installed equipment on this model.
The starting system is designed to provide the vehi-
cle operator with a convenient, efficient and reliable
means of cranking and starting the internal combus-
tion engine used to power the vehicle and all of its
accessory systems from within the safe and secure
confines of the passenger compartment. See the own-
er's manual in the vehicle glove box for more infor-
mation and instructions on the recommended use
and operation of the factory-installed starting sys-
tem.
The starting system consists of the following com-
ponents:
²Battery
²Starter relay
²Starter motor (including an integral starter sole-
noid)
²Ignition switch
²Park/neutral position switch
²Wire harnesses and connections (including the
battery cables).
This group provides complete service information
for the starter motor and the starter relay. Complete
service information for the other starting system
components can be located as follows:
²Refer toBatteryin the proper section of Group
8A - Battery for complete service information for the
battery.
²Refer toIgnition Switch and Key Lock Cyl-
inderin the proper section of Group 8D - Ignition
System for complete service information for the igni-
tion switch.²Refer toPark/Neutral Position Switchin the
proper section of Group 21 - Transmission for com-
plete service information for the park/neutral posi-
tion switch.
²Refer to the proper section ofGroup 8W - Wir-
ing Diagramsfor complete service information and
circuit diagrams for the starting system wiring com-
ponents.
Group 8A covers the Battery, Group 8B covers the
Starting Systems, and Group 8C covers the Charging
System. We have separated these systems to make it
easier to locate the information you are seeking
within this Service Manual. However, when attempt-
ing to diagnose any of these systems, it is important
that you keep their interdependency in mind.
The battery, starting, and charging systems in the
vehicle operate with one another, and must be tested
as a complete system. In order for the vehicle to start
and charge properly, all of the components that are
used in these systems must perform within specifica-
tions.
The diagnostic procedures used in each of these
groups include the most basic conventional diagnostic
methods, to the more sophisticated On-Board Diag-
nostics (OBD) built into the Powertrain Control Mod-
ule (PCM). Use of an induction-type milliampere
ammeter, volt/ohmmeter, battery charger, carbon pile
rheostat (load tester), and 12-volt test lamp may be
required.
All OBD-sensed systems are monitored by the
PCM. Each monitored circuit is assigned a Diagnos-
tic Trouble Code (DTC). The PCM will store a DTC in
electronic memory for any failure it detects. Refer to
On-Board Diagnostic Test For Charging System
in the Diagnosis and Testing section of Group 8C -
Charging System for more information.
WJSTARTING 8F - 29

switch is turned to the Off position, whichever occurs
first.
²Actuator Test- Each time the cluster is put
through the actuator test, the transmission over-tem-
perature indicator will be turned on for the duration
of the test to confirm the functionality of the bulb
and the cluster control circuitry.
The PCM or TCM continually monitors the trans-
mission temperature sensor to determine the trans-
mission operating condition. The PCM or TCM then
sends the proper trans over-temp indicator lamp-on
or lamp-off messages to the instrument cluster. If the
transmission over-temperature indicator fails to light
during the bulb test, replace the bulb with a known
good unit. If the instrument cluster turns on the
transmission over-temperature indicator due to a
high transmission oil temperature condition, it may
indicate that the transmission or the transmission
cooling system are being overloaded or that they
require service. For further diagnosis of the trans-
mission over-temperature indicator or the instrument
cluster circuitry that controls the indicator, (Refer to
8 - ELECTRICAL/INSTRUMENT CLUSTER - DIAG-
NOSIS AND TESTING). For proper diagnosis of the
transmission temperature sensor, the PCM, the
TCM, the PCI data bus, or the electronic message
inputs to the instrument cluster that control the
transmission over-temperature indicator, a DRBIIIt
scan tool is required. Refer to the appropriate diag-
nostic information.
TURN SIGNAL INDICATOR
DESCRIPTION
Two turn signal indicators, one right and one left,
are standard equipment on all instrument clusters.
The turn signal indicators are located near the upper
edge of the instrument cluster, the left one is left of
the tachometer, and the right one is right of the
speedometer. Each turn signal indicator consists of
an International Control and Display Symbol icon for
ªTurn Warningº imprinted on a green lens. Each lens
is located behind a dedicated cutout in the opaque
layer of the instrument cluster overlay. The dark
outer layer of the overlay prevents these icons from
being clearly visible when they are not illuminated.
The icons appear silhouetted against a green field
through the translucent outer layer of the overlay
when the indicator is illuminated from behind by a
replaceable incandescent bulb and bulb holder unit
located on the instrument cluster electronic circuit
board. The turn signal indicator lenses are serviced
as a unit with the instrument cluster lens, hood and
mask unit.
OPERATION
The turn signal indicators give an indication to the
vehicle operator that the turn signal (left or right
indicator flashing) or hazard warning (both left and
right indicators flashing) have been selected and are
operating. These indicators are controlled by two
individual hard wired inputs from the combination
flasher circuitry to the instrument cluster electronic
circuit board. Each turn signal indicator bulb is
grounded on the instrument cluster electronic circuit
board at all times; therefore, these indicators remain
functional regardless of the ignition switch position.
Each indicator bulb will only illuminate when it is
provided with battery current by the combination
flasher in the Junction Block (JB).
The turn signal indicators are connected in parallel
with the other turn signal circuits. This arrangement
allows the turn signal indicators to remain func-
tional, regardless of the condition of the other cir-
cuits in the turn signal and hazard warning systems.
The combination flasher outputs to the instrument
cluster turn signal indicator inputs can be diagnosed
using conventional diagnostic tools and methods. For
more information on the turn signal and hazard
warning system, (Refer to 8 - ELECTRICAL/LAMPS/
LIGHTING - EXTERIOR - OPERATION - TURN
SIGNAL & HAZARD WARNING SYSTEM).
DIAGNOSIS AND TESTING - TURN SIGNAL
INDICATOR
The diagnosis found here addresses an inoperative
turn signal indicator condition. If the problem being
diagnosed is related to inoperative turn signal or
hazard warning lamps, be certain to repair the turn
signal and hazard warning system before attempting
to diagnose or repair the turn signal indicators.
(Refer to 8 - ELECTRICAL/LAMPS/LIGHTING -
EXTERIOR - DIAGNOSIS AND TESTING - TURN
SIGNAL & HAZARD WARNING SYSTEM). If no
turn signal and hazard warning system problem is
found, the following procedure will help locate an
open in the turn signal indicator circuit. Refer to the
appropriate wiring information. The wiring informa-
tion includes wiring diagrams, proper wire and con-
nector repair procedures, details of wire harness
routing and retention, connector pin-out information
and location views for the various wire harness con-
nectors, splices and grounds.
WJINSTRUMENT CLUSTER 8J - 33
TRANS TEMP INDICATOR (Continued)

The RKE system includes two transmitters when
the vehicle is shipped from the factory, but the sys-
tem can retain the vehicle access codes of up to four
transmitters. The transmitter codes are retained in
the RKE receiver memory, even if the battery is dis-
connected. If an RKE transmitter is faulty or lost,
new transmitter vehicle access codes can be pro-
grammed into the system using a DRBIIItscan tool
and the appropriate diagnostic information.
This vehicle also offers several customer program-
mable features, which allows the selection of several
optional electronic features to suit individual prefer-
ences. (Refer to 8 - ELECTRICAL/OVERHEAD CON-
SOLE/ELECTRONIC VEHICLE INFO CENTER -
DESCRIPTION). Customer programmable feature
options affecting the RKE system include:
²Remote Unlock- Allows the option of having
only the driver side front door unlock when the RKE
transmitter Unlock button is depressed the first time
and the remaining doors and the liftgate unlock
when the button is depressed a second time, or hav-
ing all doors and the liftgate unlock upon the first
depression of the RKE transmitter Unlock button.
²Remote Linked to Memory- If the vehicle is
equipped with the Memory System, this feature
allows the option of having the RKE transmitter
Unlock button activate the recall of the stored set-
tings, or having the recall function assigned solely to
the memory switch on the driver side front door trim
panel.
²Sound Horn on Lock- Allows the option of
having the horn sound a short chirp as an audible
verification that the doors have locked, or having no
audible verification.
²Flash Lights with Lock- Allows the option of
having the lights flash as an optical verification that
the doors have locked, or having no optical verifica-
tion.
This group covers the following components of the
RKE system:
²RKE Receiver
²RKE Transmitter
Certain functions and features of the RKE system
rely upon resources shared with other electronic
modules in the vehicle over the Programmable Com-
munications Interface (PCI) data bus network. The
PCI data bus network allows the sharing of sensor
information. This helps to reduce wire harness com-
plexity, internal controller hardware, and component
sensor current loads. At the same time, this system
provides increased reliability, enhanced diagnostics,
and allows the addition of many new feature capabil-
ities. For diagnosis of these electronic modules or of
the PCI data bus network, the use of a DRBIIItscan
tool and the appropriate diagnostic information are
required.The other electronic modules that may affect RKE
system operation are as follows:
²Body Control Module (BCM)- (Refer to 8 -
ELECTRICAL/ELECTRONIC CONTROL MOD-
ULES/BODY CONTROL/CENTRAL TIMER MOD-
ULE - DESCRIPTION).
²Driver Door Module (DDM)- (Refer to 8 -
ELECTRICAL/ELECTRONIC CONTROL MOD-
ULES/DOOR MODULE - DESCRIPTION).
²Electronic Vehicle Information Center
(EVIC)- (Refer to 8 - ELECTRICAL/OVERHEAD
CONSOLE/ELECTRONIC VEHICLE INFO CENTER
- DESCRIPTION).
²Passenger Door Module (PDM)- (Refer to 8 -
ELECTRICAL/ELECTRONIC CONTROL MOD-
ULES/DOOR MODULE - DESCRIPTION).
²Powertrain Control Module (PCM)- (Refer
to 8 - ELECTRICAL/ELECTRONIC CONTROL
MODULES/POWERTRAIN CONTROL MODULE -
DESCRIPTION).
Hard wired circuitry connects the RKE system
components via the PDM to the electrical system of
the vehicle. These hard wired circuits are integral to
several wire harnesses, which are routed throughout
the vehicle and retained by many different methods.
These circuits may be connected to each other, to the
vehicle electrical system and to the RKE system com-
ponents through the use of a combination of soldered
splices, splice block connectors, and many different
types of wire harness terminal connectors and insu-
lators. Refer to the appropriate wiring information.
The wiring information includes wiring diagrams,
proper wire and connector repair procedures, further
details on wire harness routing and retention, as well
as pin-out and location views for the various wire
harness connectors, splices and grounds.
COMBINATION FLASHER
The combination flasher is a smart relay that func-
tions as both the turn signal system and the hazard
warning system flasher. The combination flasher con-
tains active electronic Integrated Circuitry (IC) ele-
ments. This flasher can be energized by the BCM to
flash all of the park/turn signal/front side marker
lamps as an optical alert for the RKE panic function
and, if the Flash Lights with Lock programmable fea-
ture is enabled, as an optical verification for the RKE
lock event. (Refer to 8 - ELECTRICAL/LAMPS/
LIGHTING - EXTERIOR/COMBINATION FLASHER
- DESCRIPTION).
HORN RELAY
The horn relay is a electromechanical device that
switches battery current to the horn when the horn
switch grounds the relay coil. The horn relay is
located in the Power Distribution Center (PDC) in
WJPOWER LOCKS 8N - 3
POWER LOCKS (Continued)

²Ten-way power drivers and passenger seats
with Memory- This power seat option is standard
on Overland models and optional on Limited models.
This option includes a six-way adjustable seat cush-
ion track with power seat back recliners and power
lumbar supports. Heated Seats are standard with
this option.
Refer toHeated Seat Systemfor more informa-
tion on the heated seat option. Refer toMemory
Systemin the Memory System section of this group
for more information on the memory system.
The power seat system includes the following com-
ponents:
²Power lumbar adjuster (ten-way power seat
only)
²Power lumbar switch (ten-way power seat only)
²Power seat recliner (ten-way power seat only)
²Power seat switch
²Power seat track.
Refer toPower Seatin Wiring Diagrams for com-
plete circuit diagrams. Following are general descrip-
tions of the major components in the power seat/
memory seat system.
DESCRIPTION - MEMORY SYSTEM
An electronic memory system is standard equip-
ment on the Limited model. The memory system is
able to store and recall the driver side power seat
positions (including the power recliner position), and
both outside power mirror positions for two drivers.
For vehicles with a radio connected to the Program-
mable Communications Interface (PCI) data bus net-
work, the memory system is also able to store and
recall up to twenty - ten AM and ten FM - radio sta-
tion presets for two drivers. The memory system also
will store and recall the last station listened to for
each driver, even if it is not one of the twenty preset
stations.
The memory system will automatically return to
all of these settings when the corresponding num-
bered and color-coded button (Driver 1 - Black, or
Driver 2 - Gray) of the memory switch on the driver
side front door trim panel is depressed, or when the
doors are unlocked using the corresponding num-
bered and color-coded (Driver 1 - Black, or Driver 2 -
Gray) Remote Keyless Entry (RKE) transmitter. A
customer programmable feature of the memory sys-
tem allows the RKE recall of memory features to be
disabled in cases where there are more than two
drivers of the vehicle.
The memory system also has a customer program-
mable easy exit feature that will move the driver
seat rearward 55 millimeters (two inches) or to the
end of its travel, whichever occurs first, when the key
is removed from the ignition switch lock cylinder.A Memory Seat Module (MSM) or Memory Heated
Seat Module (MHSM) are used on this model to con-
trol and integrate the many electronic functions and
features included in the memory system. On vehicles
equipped with the heated seat system option, the
MHSM also controls the functions and features of
that system.
The memory system includes the following compo-
nents:
²Memory seat module (or memory heated seat
module)
²Memory switch
²Position potentiometers on both outside power
mirrors
²Position potentiometers on the driver side power
seat track and power seat recliner motors.
²Radio receiver (if PCI data bus capable).
Certain functions and features of the memory sys-
tem rely upon resources shared with other electronic
modules in the vehicle over the Programmable Com-
munications Interface (PCI) data bus network. The
PCI data bus network allows the sharing of sensor
information. This helps to reduce wire harness com-
plexity, internal controller hardware, and component
sensor current loads. At the same time, this system
provides increased reliability, enhanced diagnostics,
and allows the addition of many new feature capabil-
ities. For diagnosis of these electronic modules or of
the PCI data bus network, the use of a DRBtscan
tool and the proper Diagnostic Procedures manual
are recommended.
The other electronic modules that may affect mem-
ory system operation are as follows:
²Body Control Module (BCM)- Refer toBody
Control Modulein Electronic Control Modules for
more information.
²Driver Door Module (DDM)- Refer toDoor
Modulein Electronic Control Modules for more
information.
²Electronic Vehicle Information Center
(EVIC)- Refer toElectronic Vehicle Information
Centerin Overhead Console Systems for more infor-
mation.
²Passenger Door Module (PDM)- Refer to
Door Modulein Electronic Control Modules for
more information.
²Powertrain Control Module (PCM)- Refer to
Powertrain Control Modulein Electronic Control
Modules for more information.
²Radio Receiver- Refer toRadio Receiverin
Audio Systems for more information.
Refer toHeated Seat Systemfor more informa-
tion on this system. Refer toRemote Keyless Entry
Systemin Power Lock Systems for more information
on the RKE system. Refer toPower Mirrorin
Power Mirror Systems for more information on the
WJPOWER SEAT SYSTEM 8N - 19
POWER SEAT SYSTEM (Continued)

ods may not prove conclusive in the diagnosis of the
Body Control Module (BCM), the Rain Sensor Mod-
ule (RSM), the Powertrain Control Module (PCM) or
the inputs to or outputs from these modules that con-
trol the various front wiper and washer system oper-
ating modes. The most reliable, efficient, and
accurate means to diagnose the BCM, the RSM, the
PCM or the BCM inputs and outputs related to the
various front wiper and washer system operating
modes requires the use of a DRBIIItscan tool. Refer
to the appropriate diagnostic information.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE SUPPLEMENTAL RESTRAINT
SYSTEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, DRIVER AIRBAG,
PASSENGER AIRBAG, SIDE CURTAIN AIRBAG,
FRONT IMPACT SENSOR, SIDE IMPACT SENSOR,
OR INSTRUMENT PANEL COMPONENT DIAGNOSIS
OR SERVICE. DISCONNECT AND ISOLATE THE
BATTERY NEGATIVE (GROUND) CABLE, THEN
WAIT TWO MINUTES FOR THE SYSTEM CAPACI-
TOR TO DISCHARGE BEFORE PERFORMING FUR-
THER DIAGNOSIS OR SERVICE. THIS IS THE ONLY
SURE WAY TO DISABLE THE SUPPLEMENTAL
RESTRAINT SYSTEM. FAILURE TO TAKE THE
PROPER PRECAUTIONS COULD RESULT IN ACCI-
DENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
FRONT WASHER SYSTEM
The diagnosis found here addresses an electrically
inoperative washer system. If the washer pump/mo-
tor operates, but no washer fluid is emitted from the
front washer nozzles, be certain to check the fluid
level in the reservoir. Also inspect the front washer
system components as required. (Refer to 8 - ELEC-
TRICAL/FRONT WIPERS/WASHERS - INSPEC-
TION). Refer to the appropriate wiring information.
The wiring information includes wiring diagrams,
proper wire and connector repair procedures, details
of wire harness routing and retention, connector pin-
out information and location views for the various
wire harness connectors, splices and grounds.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE SUPPLEMENTAL RESTRAINT
SYSTEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, DRIVER AIRBAG,
PASSENGER AIRBAG, SIDE CURTAIN AIRBAG,
FRONT IMPACT SENSOR, SIDE IMPACT SENSOR,
OR INSTRUMENT PANEL COMPONENT DIAGNOSIS
OR SERVICE. DISCONNECT AND ISOLATE THE
BATTERY NEGATIVE (GROUND) CABLE, THEN
WAIT TWO MINUTES FOR THE SYSTEM CAPACI-
TOR TO DISCHARGE BEFORE PERFORMING FUR-THER DIAGNOSIS OR SERVICE. THIS IS THE ONLY
SURE WAY TO DISABLE THE SUPPLEMENTAL
RESTRAINT SYSTEM. FAILURE TO TAKE THE
PROPER PRECAUTIONS COULD RESULT IN ACCI-
DENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
(1) Turn the ignition switch to the On position.
Turn the control knob on the control stalk of the
right (wiper) multi-function switch to the Low or
High wiper position. Check whether the front wiper
system is operating. If OK, go to Step 2. If not OK,
test and repair the front wiper system before con-
tinuing with these tests. Refer to FRONT WIPER
SYSTEM
(2) Turn the control knob on the control stalk of
the right (wiper) multi-function switch to the Off
position. Pull the control stalk of the right (wiper)
multi-function switch toward the steering wheel to
close the front washer switch. The front washer
pump should operate and the front wipers should
operate for about three sweep cycles after the switch
is released before they park. If the front wipers are
OK, but the front washers are not, go to Step 3. If
the front washers are OK, but the front wipers are
not, go to Step 5.
(3) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Disconnect the left headlamp and dash wire harness
connector for the front washer pump/motor from the
pump/motor connector receptacle. Check for continu-
ity between the ground circuit cavity of the left head-
lamp and dash wire harness connector for the front
washer pump/motor and a good ground. There should
be continuity. If OK, go to Step 4. If not OK, repair
the open ground circuit to ground (G106) as required.
(4) Reconnect the battery negative cable. Turn the
ignition switch to the On position. While pulling the
control stalk of the right (wiper) multi-function
switch toward the steering wheel to close the front
washer switch, check for battery voltage at the
washer pump switch sense circuit cavity of the left
headlamp and dash wire harness connector for the
front washer pump/motor unit. If OK, replace the
faulty front washer pump/motor. If not OK, repair
the open washer pump switch sense circuit between
the right (wiper) multi-function switch and the front
washer pump/motor unit as required.
(5) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Disconnect the instrument panel wire harness con-
nector (Connector C2) for the Body Control Module
(BCM) from the BCM connector receptacle. Recon-
nect the battery negative cable. Turn the ignition
switch to the On position. While pulling the control
stalk of the right (wiper) multi-function switch
toward the steering wheel to close the front washer
WJFRONT WIPERS/WASHERS 8R - 7
FRONT WIPERS/WASHERS (Continued)

function switch provides a resistor multiplexed out-
put to the Body Control Module (BCM) on a
windshield wiper switch mux circuit, and the BCM
responds by energizing the wiper on/off relay in the
Power Distribution Center (PDC) to operate the front
wiper motor momentarily at low speed to provide the
front wiper mist mode.
²Intermittent Front Wipe Mode- On models
not equipped with the optional automatic wiper sys-
tem, the control knob on the end of the right (wiper)
multi-function switch control stalk is rotated to one
of five minor intermediate detents to select the
desired intermittent front wipe delay interval. The
control knob is rotated rearward (counterclockwise)
to increase the delay, or forward (clockwise) to
decrease the delay. The right (wiper) multi-function
switch provides a resistor multiplexed output to the
Body Control Module (BCM) on a windshield wiper
switch mux circuit. The BCM responds by monitoring
electronic vehicle speed messages received from the
Powertrain Control Module (PCM) over the Program-
mable Communications Interface (PCI) data bus,
then energizing the wiper on/off relay in the Power
Distribution Center (PDC) to operate the front wiper
motor at the proper delay intervals.
²Intermittent Rear Wipe Mode- The control
ring on the right (wiper) multi-function switch con-
trol stalk is rotated to the center detent to select the
intermittent rear wiper mode. The right (wiper)
multi-function switch provides a battery current out-
put to the rear wiper motor on a rear wiper motor
delay control circuit to signal the rear wiper module
to operate the rear wiper in the intermittent wipe
mode.
²Rear Washer Mode- The right (wiper) multi-
function switch control stalk is pushed forward
toward the instrument panel to a momentary posi-
tions to activate the rear washer pump/motor in the
rear washer mode. The rear washer pump will con-
tinue to operate in the rear washer mode until the
control stalk is released. The right (wiper) multi-
function switch provides battery current on a rear
washer pump motor control circuit to energize the
rear washer pump in the rear washer mode.DIAGNOSIS AND TESTING - RIGHT MULTI-
FUNCTION SWITCH
Be certain to perform the diagnosis for the front
wiper system, front washer system, rear wiper sys-
tem, and/or rear washer system before testing the
right multi-function switch. (Refer to 8 - ELECTRI-
CAL/FRONT WIPERS/WASHERS - DIAGNOSIS
AND TESTING) or (Refer to 8 - ELECTRICAL/REAR
WIPERS/WASHERS - DIAGNOSIS AND TESTING).
Refer to the appropriate wiring information. The wir-
ing information includes wiring diagrams, proper
wire and connector repair procedures, details of wire
harness routing and retention, connector pin-out
information and location views for the various wire
harness connectors, splices and grounds.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE PASSIVE RESTRAINT SYS-
TEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, DRIVER AIRBAG,
PASSENGER AIRBAG. SIDE CURTAIN AIRBAG,
FRONT IMPACT SENSOR, SIDE IMPACT SENSOR,
OR INSTRUMENT PANEL COMPONENT DIAGNOSIS
OR SERVICE. DISCONNECT AND ISOLATE THE
BATTERY NEGATIVE (GROUND) CABLE, THEN
WAIT TWO MINUTES FOR THE SYSTEM CAPACI-
TOR TO DISCHARGE BEFORE PERFORMING FUR-
THER DIAGNOSIS OR SERVICE. THIS IS THE ONLY
SURE WAY TO DISABLE THE PASSIVE RESTRAINT
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the right multi-function switch from
the steering column and disconnect the instrument
panel wire harness connector for the switch from the
switch connector receptacle.
(3) Using an ohmmeter, check the right multi-func-
tion switch continuity and resistances at the switch
terminals as shown in the Right Multi-Function
Switch test chart (Fig. 17).
8R - 22 FRONT WIPERS/WASHERSWJ
RIGHT MULTI-FUNCTION SWITCH (Continued)

The other two heater elements (downstream sen-
sors 1/2 and 2/2) are controlled by the downstream
heater relay through output signals from the PCM.
To avoid a large simultaneous current surge, power
is delayed to the 2 downstream heater elements by
the PCM for approximately 2 seconds.
REMOVAL
(1) Remove PDC cover.
(2) Remove relay from PDC.
(3) Check condition of relay terminals and PDC
connector terminals for damage or corrosion. Repair
if necessary before installing relay.
(4) Check for pin height (pin height should be the
same for all terminals within the PDC connector).
Repair if necessary before installing relay.
INSTALLATION
(1) Install relay to PDC.
(2) Install cover to PDC.
O2S SENSOR
DESCRIPTION
The Oxygen Sensors (O2S) are attached to, and
protrude into the vehicle exhaust system. Depending
on the emission package, the vehicle may use a total
of either 2 or 4 sensors.
Federal Emissions Package:Two sensors are
used: upstream (referred to as 1/1) and downstream
(referred to as 1/2). With this emission package, the
upstream sensor (1/1) is located just before the main
catalytic convertor. The downstream sensor (1/2) is
located just after the main catalytic convertor.
4.7L V-8 With California Emissions Package:
On this emissions package, 4 sensors are used: 2
upstream (referred to as 1/1 and 2/1) and 2 down-
stream (referred to as 1/2 and 2/2). With this emis-
sion package, the right upstream sensor (2/1) is
located in the right exhaust downpipe just before the
mini-catalytic convertor. The left upstream sensor
(1/1) is located in the left exhaust downpipe just
before the mini-catalytic convertor. The right down-
stream sensor (2/2) is located in the right exhaust
downpipe just after the mini-catalytic convertor, and
before the main catalytic convertor. The left down-
stream sensor (1/2) is located in the left exhaust
downpipe just after the mini-catalytic convertor, and
before the main catalytic convertor.
4.0L 6±Cylinder With California Emissions
Package:On this emissions package, 4 sensors are
used: 2 upstream (referred to as 1/1 and 2/1) and 2
downstream (referred to as 1/2 and 2/2). With this
emission package, the rear/upper upstream sensor
(2/1) is located in the exhaust downpipe just beforethe rear mini-catalytic convertor. The front/upper
upstream sensor (1/1) is located in the exhaust down-
pipe just before the front mini-catalytic convertor.
The rear/lower downstream sensor (2/2) is located in
the exhaust downpipe just after the rear mini-cata-
lytic convertor, and before the main catalytic conver-
tor. The front/lower downstream sensor (1/2) is
located in the exhaust downpipe just after the front
mini-catalytic convertor, and before the main cata-
lytic convertor.
OPERATION
An O2 sensor is a galvanic battery that provides
the PCM with a voltage signal (0-1 volt) inversely
proportional to the amount of oxygen in the exhaust.
In other words, if the oxygen content is low, the volt-
age output is high; if the oxygen content is high the
output voltage is low. The PCM uses this information
to adjust injector pulse-width to achieve the
14.7±to±1 air/fuel ratio necessary for proper engine
operation and to control emissions.
The O2 sensor must have a source of oxygen from
outside of the exhaust stream for comparison. Cur-
rent O2 sensors receive their fresh oxygen (outside
air) supply through the O2 sensor case housing.
Four wires (circuits) are used on each O2 sensor: a
12±volt feed circuit for the sensor heating element; a
ground circuit for the heater element; a low-noise
sensor return circuit to the PCM, and an input cir-
cuit from the sensor back to the PCM to detect sen-
sor operation.
Oxygen Sensor Heaters/Heater Relays:
Depending on the emissions package, the heating ele-
ments within the sensors will be supplied voltage
from either the ASD relay, or 2 separate oxygen sen-
sor relays. Refer to Wiring Diagrams to determine
which relays are used.
The O2 sensor uses a Positive Thermal Co-efficient
(PTC) heater element. As temperature increases,
resistance increases. At ambient temperatures
around 70ÉF, the resistance of the heating element is
approximately 4.5 ohms on 4.0L engines. It is
approximately 13.5 ohms on the 4.7L engine. As the
sensor's temperature increases, resistance in the
heater element increases. This allows the heater to
maintain the optimum operating temperature of
approximately 930É-1100ÉF (500É-600É C). Although
the sensors operate the same, there are physical dif-
ferences, due to the environment that they operate
in, that keep them from being interchangeable.
Maintaining correct sensor temperature at all
times allows the system to enter into closed loop
operation sooner. Also, it allows the system to remain
in closed loop operation during periods of extended
idle.
14 - 50 FUEL INJECTIONWJ
O2S HEATER RELAY (Continued)

(5) Install the new diode in the harness, making
sure current flow is correct. If necessary refer to the
appropriate wiring diagram for current flow.
(6) Solder the connection together using rosin core
type solder only.Do not use acid core solder.
(7) Tape the diode to the harness using electrical
tape making, sure the diode is completely sealed
from the elements.
(8) Re-connect the battery, and test affected sys-
tems.SPECIFICATIONS
A/C APPLICATION TABLE
Item Description Notes
VEHICLE WJ - Grand
Cherokee
SYSTEM R134a w/
expansion valve
COMPRESSOR Nippondenso
10PA17ND-8 PAG oil
Freeze±up
ControlEvaporator Probe Evaporator
mounted
Low psi Control opens < 22 psi -
resets > 34-38 psi
High psi Control opens > 450-490
psi - resets <
270-330 psiline mounted
CONTROL
HEADManual type manual
controls
Automatic Zone
Control (AZC)Automatic
Zone Control
(AZC) with
dual infrared
sensing
Mode Doors Vacuum actuators
(manual)electric
actuator
(AZC)
Blend Door Electric actuator (manual and
AZC)
Blend Door
(passenger)Electric actuator (AZC only)
Recirculation
DoorVacuum actuator
(manual)electric
actuator
(AZC)
Blower Motor Hardwired to
control head
resistor block
(manual),
blower
controller (AZC)
COOLING FAN Hybrid - viscous
clutch/electricPCM output
CLUTCH
Control Relay PCM
controlled
Draw
2.0-3.9 amps @ 12 V  0.5V@ 70É F
Gap 0.0169-0.0319
DRB IIIT
Reads TPS, RPM, A/C
switch
Actuators Clutch relay
WJHEATING & AIR CONDITIONING 24 - 7
HEATING & AIR CONDITIONING (Continued)

A/C COMPRESSOR CLUTCH
DESCRIPTION
The compressor clutch assembly consists of a sta-
tionary electromagnetic coil, a hub bearing and pul-
ley assembly, and a clutch plate (Fig. 4). The
electromagnetic coil unit and the hub bearing and
pulley assembly are each retained on the nose of the
compressor front housing with snap rings. The clutch
plate is keyed to the compressor shaft and secured
with a bolt.
OPERATION
The compressor clutch components provide the
means to engage and disengage the compressor from
the engine serpentine accessory drive belt. When the
clutch coil is energized, it magnetically draws the
clutch into contact with the pulley and drives the
compressor shaft. When the coil is not energized, the
pulley freewheels on the clutch hub bearing, which is
part of the pulley. The compressor clutch and coil are
the only serviced parts on the compressor.
The compressor clutch engagement is controlled by
several components: the a/c switch on the a/c heater
control panel, the Automatic Zone Control (AZC) con-
trol module (if the vehicle is so equipped), the evap-
orator probe, the a/c high pressure transducer, the
a/c compressor clutch relay, the body control module
(BCM) and the Powertrain Control Module (PCM).
The PCM may delay compressor clutch engagement
for up to thirty seconds. Refer to Electronic Control
Modules for more information on the PCM controls.
DIAGNOSIS AND TESTING - COMPRESSOR
CLUTCH COIL
For circuit descriptions and diagrams, refer to the
appropriate wiring diagrams. The battery must be
fully-charged before performing the following tests.
Refer to Battery for more information.
(1) Connect an ammeter (0 to 10 ampere scale) in
series with the clutch coil terminal. Use a voltmeter
(0 to 20 volt scale) with clip-type leads for measuring
the voltage across the battery and the compressor
clutch coil.
(2) With the a/c heater mode control switch in any
a/c mode, the a/c heater control a/c switch in the ON
position, and the blower motor switch in the lowest
speed position, start the engine and run it at normal
idle.
(3) The compressor clutch coil voltage should read
within 0.2 volts of the battery voltage. If there is
voltage at the clutch coil, but the reading is not
within 0.2 volts of the battery voltage, test the clutch
coil feed circuit for excessive voltage drop and repair
as required. If there is no voltage reading at the
clutch coil, use a DRBIIItscan tool and the appro-
priate diagnostic information for testing of the com-
pressor clutch circuit. The following components
must be checked and repaired as required before you
can complete testing of the clutch coil:
²Fuses in the junction block and the Power Dis-
tribution Center (PDC)
²A/C heater mode control switch
²A/C compressor clutch relay
²A/C high pressure transducer
²A/C evaporator probe
²Powertrain Control Module (PCM)
²Body Control Module (BCM)
(4) The compressor clutch coil is acceptable if the
current draw measured at the clutch coil is 2.0 to 3.9
amperes with the electrical system voltage at 11.5 to
12.5 volts. This should only be checked with the work
area temperature at 21É C (70É F). If system voltage
is more than 12.5 volts, add electrical loads by turn-
ing on electrical accessories until the system voltage
drops below 12.5 volts.
(a) If the clutch coil current reading is four
amperes or more, the coil is shorted and should be
replaced.
(b) If the clutch coil current reading is zero, the
coil is open and should be replaced.
Fig. 4 COMPRESSOR CLUTCH - TYPICAL
1 - CLUTCH PLATE
2 - SHAFT KEY
3 - PULLEY
4 - COIL
5 - CLUTCH SHIMS
6 - SNAP RING
7 - SNAP RING
WJCONTROLS 24 - 13